﻿<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <title>类别选择器</title>
    <style>
        .a {
            color: blue;
            font-size: 20px;
        }

        .b {
            color: red;
            font-size: 22px;
        }
    </style>
</head>
<body>
    <h3 class=b>清明</h3>
    <p class="a">清明时节雨纷纷</p>
    <p class="b">路上行人欲断魂</p>
</body>
</html>